America's wealthiest people occupy palatial properties in exclusive zip codes.
But some of these residences are no longer simply the playgrounds of billionaires, with many have now been transformed into museums and institutions of higher education.
The properties pictured below are the largest homes ever to stand in the United States.
Many of them were built or live in by the Vanderbilt, who gained prominence during the Gilded Age with success in the shipping and railroad empires of Cornelius Vanderbilt.
30. Duke Farms, New Jersey
Duke Farms is an estate in Hillsborough Township, New Jersey, established by James Buchanan Duke, founder of the American Tobacco Company.
The estate includes the mammoth Farm Barn building and Horace Trumbauer conservatory and greenhouses known as Duke Gardens, while the mansion itself was demolished in 2016.
29. San Sylmar, California
The San Sylmar mansion, located in Sylmar, California, was founded by American entrepreneur J.B. Nethercutt in 1971.
The sprawling estate houses one of the world's greatest car collections, which become known as the Nethercutt Collection.
28. El Mirasol, Florida
El Mirasol was a 37-room Spanish Colonial Revival mansion at 348 N. Ocean Boulevard in Palm Beach, Florida, designed by architect Addison Mizner for financier Edward T. Stotesbury,
The mansion was expanded several times even after it was officially completed in 1920, and included a 40-car garage, a tea house, an auditorium, and a private zoo. El Mirasol was demolished in 1959.
27. Pembroke, New York
Built in 1916, for U.S. Senator Joseph Raphael De Lamar was an enormous mansion spread over five square kilometres of Glen Cove, New York.
The stately home was demolished in 1958, and the site now houses an exclusive gated community yacht club.
26. Gemini, Florida
The huge Gemini estate is among the most expensive real estate listings in the country and was sold for $94.17million in 2021, after six years on the market.
Located on Manalapan, just south of Palm Beach, Florida, the estate covers the entire ocean-to-lake stretch of the barrier island.
25. The Breakers, Rhode Island
The Breakers is a Gilded Age mansion built in Newport, Rhode Island, between 1893 and 1895 as a summer residence for the fabulously wealthy Cornelius Vanderbilt II.
The 70-room mansion was added to the National Register of Historic Places in 1971, and the building now operating as a museum was designated a National Historic Landmark in 1994.
24. Mar-a-Lago, Florida
Mar-a-Lago, translated from the Spanish for "sea to lake" is a lavish 126-room mansion on the Palm Beach barrier island, Florida, with the Atlantic Ocean to the east and Florida's Intracoastal Waterway to the west.
Mar-a-Lago was purchased in 1985 for a reported $10 million by Donald Trump, who converted the estate into the Mar-a-Lago Club, while maintaining private quarters in a separate, closed-off area of the grounds.
=22. Fair Field, New York
Built in 2003, Fair Field is a large private house owned by American billionaire businessman Ira Rennert in the Hamptons, Long Island.
The mansion, which is considered to be one of America's largest private homes, is thought to be valued at up to $500 million.
=22. Stan Hywet Hall, Ohio
Stan Hywet Hall & Gardens is a vast estate including one of the largest houses in the U.S.
Its name loosely translates from the Old English for "stone quarry," and it was erected between 1912 and 1915 for F.A. Seiberling, co-founder of the Goodyear Tire and Rubber Company.
21. Xanadu 2.0, Lake Washington
Microsoft founder Bill and Melinda Gates own this mammoth mansion on their lake front estate in the Seattle suburbs, valued at upward of $131 million.
The sprawling complex—rumoured to include a spa, a 60ft pool, a gym paneled with stone from a mountain peak in the Pacific Northwest, a trampoline room, and a stream for salmon, trout and other fish—was dubbed Xanadu 2.0 by Bill Gates' biographer.
20. Grey Towers Castle, Pennsylvania
Grey Towers Castle is a Gilded Age building situated on the campus of Arcadia University in Glenside, Pennsylvania.
The epically proportioned property, which was designed by prominent American architect Horace Trumbauer when he was just 23 years old, was designated a National Historic Landmark in 1985 for its eclectic yet elegant designs.
19. Hearst Castle, California
Publishing baron William Randolph Hearst began building an opulent estate on his ranchland overlooking the village of San Simeon in 1919.
By 1947, the hilltop complex dubbed "La Cuesta Encantada", Spanish for The Enchanted Hill, included a twin-towered main building, three sprawling guesthouses and approximately 127 acres of terraced gardens, fountains, and pools.
18. Lynnewood Hall, Pennsylvania
This 110-room Neoclassical Revival vacant mansion in Elkins Park, Montgomery County, and designed for U.S. tycoon Peter A. B. Widener
This turn-of-the-century estate was large enough to feature an art gallery and a ballroom large enough to accommodate 1,000 guests before it tragically fell into disrepair.
17. Woodlea, Briarcliff Manor, New York
Woodlea is a 140-room mansion on the tHudson River's banks, which is believed to have been the 15th largest private house in America at the time of its construction.
Completed in 1895, for New York State Bar Association founder Elliott Fitch Shepard's wife Maggie, the building was reportedly inspired by Kimberley Hall in England, the ancestral home of P.G Wodehouse.
16. Idle Hour, New York
Idle Hour, located in Oakdale on Long Island, was completed in 1901 for American businessman and heir William Vanderbilt.
At the time of its completion, the mansion was tied 15th for the largest house in the U.S.
15. Inisfada, New York
The sprawling Inisfada Tudor castle was once situated on 30 acres on Nassau County's North Hills.
Built for New York City businessman Nicholas Frederic Brady in 1920, the 87 room home was later given to Jesuits, before the estate was demolished in December 2013.
14. Pensmore, Missouri
Located in the Ozark Mountains, Pensmore, is one of the largest homes in the U.S., built for its owner, American multi-millionaire astrophysicist, Steven Huff.
The building, which is reportedly still is under construction, boasts five-story-tall towers, 13 bedrooms and exterior walls 12-inches thick, which have been designed to survive earthquakes, tornadoes and even bomb blasts.
13. Indian Neck Hall, New York
Reputed to have been the largest estate on Long Island when it was completed in 1897, Indian Neck Hall was designed as the home for Singer Manufacturing Company president Frederick Gilbert Bourne.
The Georgian-style home was in 1926 opened as the LaSalle Military Academy, before being sold to St. John's University in 2001.
12. Harbor Hill, New York
Completed in 1902, the Harbor Hill estate contained at the time the largest home he ever designed, and was built to emulate the style of a French castle.
However, after the stock market crash of 1929, Harbor Hill's massive acreage soon became impossibly expensive to maintain by its multi-millionaire owners, and the building was eventually demolished in 1947.
11. Florham, New Jersey
Found in Madison, the 110-room Florham was built during the 1890s as a country estate for members of the Vanderbilt family.
The architects were instructed to build "a house on the order of an English country gentleman...a thoroughly comfortable house, without the stiffness of the modern city house."
10. Versailles, Florida
This 108,381-square-foot mega-mansion in Windermere, Florida, is scheduled to be completed in the middle of 2022.
The Florida mansion, which will have 13 bedrooms and 23 bathrooms, was inspired by the Palace of Versailles in France and is owned by the founder of Orlando-based time-share company Westgate Resorts, David Siegel and wife Jackie Siegel.
9. Meadow Brook Hall, Michigan
Constructed between 1926 and 1929 for $4 million, Meadow Brook Hall is still considered one of the finest examples of Tudor-revival architecture in the U.S.
This historic 110-room home was built by the widow of automobile pioneer John Dudge and the property is counted as one of America's Castles and named as a National Historic Landmark in 2012.
8. Shadow Lawn, New Jersey
Shadow Lawn is a historic house on the campus of Monmouth Universit, built in 1927.
The large masonry building, which was featured heavily in the movie Annie, was one of the last of its kind to be built before the Great Depression and was designated a National Historic Landmark in 1985 for its architecture.
7. Cornelius Vanderbilt II House, New York
Built in 1883, this large mansion once occupied the frontage along the west side of New York's Fifth Avenue from West 57th Street up to West 58th Street.
The mansion was, and remains, the largest private residence ever built in New York City; however, the home was sold in 1926 and demolished to make way for a department store.
6. Winterthur, Delaware
This former home of renowned antique dealer Henry Francis du Pont in the town of Winterthur was constructed in the early 20th century.
The sprawling private home, situated on a 979-acre estate now houses one of the most important collections of Americana in the U.S.
5. Arden House, New York
Arden is a historic estate outside New York, once owned by railroad magnate Edward Harriman, who at the time of its construction possessed 63 square miles of the area.
The mansion, which was approached by a three-mile-long carriage drive, now operates as a conference center with 97 guest rooms.
4. Whitemarsh Hall, Pennsylvania
Completed in 1921 for investment banker Edward Stotesbury and his family, Whitemarsh Hall reportedly represented the apogee of the Gilded Age.
The 147-room building is reputed to be the most expensive house built in Pennsylvania and car manufacturer Henry Ford reportedly reflected after a visit: "It's a great experience to see how the rich live."
3. The One, Los Angeles
The One, located in Bel Air, is considered the culmination of ultra-deluxe real estate developer Nile Niami's life's work.
The sprawling building is thought to have been completed in 2021, according to The Robb Report. The property is currently available for $340 million, down from the $500 million initial estimated price.
2. Oheka Castle, New York
Oheka Castle, also known as the Otto Kahn Estate, is a hotel located on the North Shore of Long Island, in a hamlet in the town of Huntington.
Completed in 1919, the former country home of investment financier Otto Hermann Kahn and his family comprising 127 rooms is now a historic hotel.
1. Biltmore Estate, North Carolina
Biltmore House is a Châteauesque-style mansion built for George Washington Vanderbilt II between 1889 and 1895 and is America's largest home.
The 250-room castle is still owned by Vanderbilt's descendants and Biltmore Estate remains one of the most prominent examples of Gilded Age mansions.
Update 09/28/21, 5:41 a.m. ET: This article has been updated with an image showing the Versailles mansion in Windermere, Florida.